Gastric Digestion and Stomach disease Flashcards
Where is food mixed and grinded?
The antrum of the stomach
What part of the stomach stores food and how does it relax?
The fundus, and is controlled by the vagus nerve.
It distends due to the vagovagal reflex allowing more food to be stored.
What does normal stomach function require?
Intact antum, pylorus and duodenum
Intact vagus nerve
Normal hormone function
How can stomach emptying be abnormal and what are examples?
Rapid emptying: can happen post surgery, causing the dumping effect. Vomitin, pain, diarrhoea and nausea are symptoms. Pain due to distensipon of SI and diarrhoea due to hyperosmolar chyme
Delayed emptying: can occur to due diabetes causing autonomic neuropathy
What does gastric acid do?
Sterilises food, and aids in vit. B12 and iron absorption
What secretes HCl, and how do they do this?
Parietal cells located in the stomach body.
They secrete it by use of the H+/K+ ATPase pump. H+ is pumped out wiht HCO3- (due to action of carbonic anhydrase) and K+ is taken in.
Cl- enters cell.
Tubovesicles fuse with canaliculi and H+ is pumped out
Where are specialised stomach cells located?
Body: Parietal cells, ECL cells
Antrum: D cells and G cells
What do ECL cells secrete and how is the signal sent?
histamine acts on parietal cells causing increased HCl secretion. paracrine route
What do G cells secrete?
Gastrin, and it travels in the bloodstream (endocrine) to target ECL cells causing more histamine and in turn more HCl
What do D cells secrete?
somatostatin, and it has endocrine and paracrine activity. It inhibits by acting on G cells preventing gastrin release
What cells do the vagus nerve innervate?
G cells, ECL cells and parietal cells, via the submucosal nerve plexi? via acetylcholine
How can gastric acid seceretion be abnormal and why?
Increased: Gastrinomas
Decreased: Gastric surgery (removal of body/antrum); Drugs that block proton pumps/histamine receptors; vagotomy; pernicious anaemia where antibodies kill parietal cells.
What are the three phases of stomach digestion?
Cephalic phase: vagus nerve stimulates cells that increase HCl production, thought of food
Gastric phase: food in stomach, gastric distension causes enteric nerve plexi to release Ach targeting cells increase HCl, aswell as amino acids stimualting G cells
Intestinal phase: food in duodenum, HCl stimulates D cells to release somatostatin, inhibiting G cells and gastrin release. Secretin and cholecystokinin relased in duodenum
What do secretin and cholecystokinin respond to, and do?
Secretin: In response to HCl, inhibit gastrin secretion and stimulates pancreas and bile ducts to release HCO3-
Cholecystokinin: in response to fats/proteins, inhibits gastrin release and causes pancreas to secrete pancreatic enzymes and gall bladder to contract releasing bile.
What is the epidemiology of H. pylori
That is prefers gastric antrum. Acts by inflamming gastric mucosa.
often occurs on childhood in poor living conditions
